METHOD OF UTILIZING FURNACE OFF-GAS FOR REDUCTION OF IRON OXIDE PELLETS

Abstract

The invention relates to the use of off-gas from furnaces (2) for the process of reduction of iron oxide. The bypass duct leads off-gas with reduction atmosphere directly into the reactor, passing through and back to join the main duct of dedusting system using negative pressure of the primary dedusting system. The off-gas directly heats up the iron oxide pellet and maintain the reduction atmosphere in the reactor and allow the reaction to proceed and prevent re-oxidation.

Claims

1. Method of Utilizing Furnace Off-gas for reduction of Iron Oxide Pellets has a bypass duct (3) leading furnace (2) off-gas directly into reactor (5) and also leads the flow back to join the main duct of primary dedusting system. The negative pressure (7) of primary dedusting system induces off-gas flow from furnace (2) passing through reactor (5). The iron oxide pellets are directly heated by the off-gas and under the reducing atmosphere in the reactor (5) provided by the off-gas and the reduction of iron oxide in the pellet can go and re-oxidation is prevented.

2. Method of Utilizing Furnace Off-gas for reduction of Iron Oxide Pellets in accordance with claim 1 where the entry of the bypass duct (3) at furnace side is made of double ducts with the inner duct leading to reactor (5) and the outer duct has suction (7) pressure to take atmospheric air and minimize the penetration into inner duct

3. Method of Utilizing Furnace Off-gas for reduction of Iron Oxide Pellets in accordance with claim 1-2 where the bypass duct (3) has dampers (4) to control inlet and outlet flow of Reactor (5).

4. Method of Utilizing Furnace Off-gas for reduction of Iron Oxide Pellets in accordance with claim 1-3 where reactor (5) is equipped with burner (6) to control temperature and reducing atmosphere.

5. Method of Utilizing Furnace Off-gas for reduction of Iron Oxide Pellets in accordance with claim 1-4 where reactor (5) is installed above the furnace (2) with some offset degree to the side so it does not block furnace operation but it still can discharge DRI into furnace by gravity.

6. Method of Utilizing Furnace Off-gas for reduction of Iron Oxide Pellets in accordance with claim 1-5 where the reactor (5) has discharging mechanism to discharge product of reaction (DRI) into furnace (2) immediately after reaction in order to taking energy contained in the DRI back to the furnace and preventing re-oxidation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 Shows the process of Method of Utilizing Furnace Off-gas for reduction of Iron Oxide Pellets

DETAILED DISCLOSURE

[0015] FIG. 1 Shows the process of Method of Utilizing Furnace Off-gas for reduction of Iron Oxide Pellets

[0016] The invention utilizes the off-gas from furnaces (2), which could be Electric Arc Furnace or Basic Oxygen Furnace or other types of furnace with reducing off-gas, for reduction of pellets incorporated with iron oxide and carbonaceous material.

[0017] The reactor (5) is located above the furnace not directly on top but offset to aside so it does not obstruct operation when charging input material into the furnace.

[0018] A portion of the off-gas is led into the inside of reactor (5) entry the bypass duct (3) and out of the reactor (5) to rejoin the primary duct. The bypass duct (3) allows utilization of existing primary suction (7) that is usually required in all furnaces (2) to induce a portion of primary off-gas flow into Reactor (5) without dedicated fan or equipment to produce suction (7) or negative pressure specifically for Reactor.

[0019] Off-gas from furnace, as it goes into Reactor (5), heats up the reactor (5) and keeps it under reducing atmosphere. At the high temperature, the reaction goes and iron oxide pellets are reduced to direct reduced iron (DRI). The re-oxidation of iron in DRI is prevented by the reducing atmosphere in the reactor (5). There is a burner (6) inside the reactor (5) to operate as supplementary to the off-gas to maintain temperature and reducing atmosphere inside the reactor (5). Discharging pallets from storage (1) into reactor (5) is made via a discharging mechanism as well as discharging of direct reduced iron into the furnace. The timing of the is to be made in the right sequence with the process of the furnace (2) in order to allowing sufficient time for melting DRI into liquid and for decarburizing to reach desired carbon content of liquid steel.

[0020] It is important that the penetrating of external air into the reactor (5) is minimized. Most of the furnaces (2) need to have movements to accommodate several steps of the steelmaking process (i.e. input material charging, de-slagging or tapping) whereas the primary dedusting system is in fixed position. This makes a split or a gap between the primary duct and the off-gas outlet of the shell is inevitable. The inlet of the bypass duct (3) is made as inner duct of primary duct, therefore, the external air coming via the gap between furnace and primary duct tends to flow along the suction (7) of primary dedusting line. The inner duct, is protected by negative pressure of the outer duct, receive mainly off-gas from the furnace. There are also dampers (4) at the inlet and outlet duct of the reactor (5) to control flow rate and to isolate the reactor (5) when required.